Circuit breaker



April 25, 1933. K c, RANDALL,

C IRCUIT BREAKER Filed April 4 193 0 3 Sheets-Sheet l INVENTOR Karl Cfiandall ATTQRNEY Apr-i125, 1933. K. c. RANDALL CIRCUIT BREAKER Filed April 4, '1930 3 Sheets-Sheet 2 1 [m7] III I II I 111 I'IIIIIIIIIIIIIIII' I VIIIIIIIIIIIIIIIIIIIIIIIIIII I INVNTOR Karl C.Randal1 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Elia/11w IIIIIIIIIIIIIIIIIIIIIII'IIIIIIIII AIIORNEY April 25, 1933. Q RANDALL 1,905,501

CIRCUIT BREAKER Filed April 1930 3 Sheets-Sheet 5 INVENTOR Karl (lRandall AT ToRNEY Patented A pr.25,1933 1,905,501

UNITED STATES PATENT-OFFICE KARL C. RANDALL, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO -'W'ES'J."INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA CIRCUIT BREAKER Application filed April 4, 1930. Serial No. 441,513.

My invention relates to circuit breakers vide a circuit breaker having the above noted and particularly to circuit breakers for con-. characteristics wherein the transformersv trolling the operation of: motors, electric serve as current-limiting agents; thereby lamps and similar apparatus. limiting the current passing through the cir- An object of my invention is to provide a cuit breaker at the time of opening under 55 circuit breaker, including a current-respon severe overload of short-circuit surges. sive device having substantially fixed oper-" These and other objects that will be made ating characteristics and operative for openapparent throughout the further description ing the circuit under predetermined current of my invention are obtained by circuitor load conditions, with means for renderbreaker apparatus hereinafter described and 60 ing the current-responsive device effective illustrated in the accompanying drawings, for opening the circuit breaker under curwherein; rent or load conditions greater or less than Figure 1 is a longitudinal section through the said predetermined current or load cona circuit breaker embodying features of my dition invention, portions of the circuit breaker be- 5 Another object of my invention is to proing shown in elevation; vide a circuit breaker having relatively large Fig. 2 is a plan viewof the circuit-breaker capacity that comprises a plurality of relaapparatus shown in Fig. 1, the housing being tively small circuit-breaker units each proshown in section;

2o vided with a current-responsive trip device Fig. 3 is a diagram showing the manner 7 having definite characteristics and relatively in which the bimetal thermal element of a low capacity and wherein the current supsingle circuit-breaker unit is connected to plied to the current-responsive devices may an auto-transformer, for rendering the cirbe divided uniformly between them or procuit breaker operable to trip open under a portioned in accordance with any predeterload less than that for which the thermal 75 mined values. element is designed to operate;

A further object of my invention is to Fig. 4 is a view, similar to Fig. 3, showprovide a circuit breaker comprising a pluing the manner in which an auto-transrality of circuit-breaker units connected in former is connected to the thermal-element parallel in each circuit to be operated by a for rendering it operable to trip only under 80 manually operable handle that is trip-free a load greater than that for which the therof the circuit breaker units and wherein the l l m t i d i d t Operate; current supplied to the current-responsive Fi 5 i a di showing a pair of 1 devlces for each Cu'cmt breaker y thermal elements of separate circuit-breaker h a predetevmlled Value thereby units connected to an auto-transformer for 85 an of the (.nrcmt e .slmulmneously distributin the current to the thermal ele- Operable to tnp to Open posltlon under merits in ii'edetermined ro ortions' determined overload or short-circuit condil d g g z to of tions' Fi 5 showin the .manner in which three 40 Afurther ob ect of my invention is to prol f t k 90 vide a polyphase clrcuit breaker wherein a erma e 5 O Sepam e clrcm Yea ers are connected to two auto-transformers for plurality of current-responsive circuit breakrs are connected in parallel ineach distributing the current between the thermal elements in predetermined proportional phase and wherein the current supplied to the current-responsive devices of each cirl cuit breaker may be proportioned in prede- E g- 7 g a of 8- termined values and wherein all of the cirll lng he m nner In Wlnch four cuit breakers may be manually operated by thermal elements of separate circuit breaka handle that is trip free of them. ers are connected to three auto-transformers Afurther object of my invention is to profor distributing the current between the 100 thermal element in predetermined proportional values and Fig. 8 is a diagram showin the manner in which 9 or more circuit breaker units may be connected in a three phase circuit in such manner that the thermal elements of the separate circuit breakers are connected to auto-transformers for uniformly distributing the current supplied thereto.

In Figs. 1 and 2, I have shown my invention applied to a Clll.'GI1t-I9SI)OI1Si\6 circuitbreaker unit, such as is disclosed in Patent No. 1,794,901, issued to O. S. Jennings, and assigned to the assignec of this application. Briefly, each circuit breaker unit comprises an insulating base 9 having a recess 11 in which a stationary contact 12 is mounted and which is adapted to be engaged by a movable contact 13 carried upon a switch arm 14 that is pivoted, at 15, upon a sheetmetal frame or bracket 16 which is mounted on the base 9 within the notch 11. The switch. arm 14 is operated by a pair of toggle links 17 and 18, that are pivoted together by a knee pivot 19. The link 17 is pivotally mounted on a shaft 21 which is carried by the switch arm 14, and the link 18 is DlVO- tally seated in a notch 22 of V shape provided in a releasable carrier 23 that is pivotally mounted on the frame 16 for rotation about a shaft 24.

The carrier 23 is releasably retained in the operable position shown in Fig. 1 by a bimetal thermal element 26 of U shape and diagrammatically illustrated in Figs. 3 to 8. inclusive. An operating lever 27 is mounted for rotation about the shalt 28 that is secured to the frame 16, and is provided with an insulating handle 29 by means of whi h the swit h may be manually operated. tension spring conncctsthe outer end the operating lever 27 to the knee pivot cf the toggle links 17 and 1S and serves 0 mo'c the toggle links to the made or tenet; positions shown in ierein the knee pivot 19 lies slightly above line connecting the shaft 21 and the pivot se: t of the link 18.

i i hen the toggle is in the made posihim the contactof the switch arm 14 is reieasablv retained in closed position, and, when the operating handle 29 has been moved downwardly a suliicient distance, the spring 31 causes the toggle to collapse and move the switch arm 1 to open position with a snap action. By reason of this construction. the switch arm is actuated to open and to closed position by the over center wring 31. when the switch or circuit breaker 1.. manually operated through the medium of lhe handle The spring 3] also tends to move the carin a clockwise direction, and, re-

oi' the position of the operating han ie. dots actually move the carrier 23p to release or trip the circuit breaker 'through the circuit breaker remains 'ing capacity of Fig. 1'

when the thermal element 26 has been heated sufficiently to move the latch 32, that is secured to its outer end, out of engagement with the free end of the carrier 23.

The bimetal element may be proportioned to open position in response to a predetermined overload or a SilUl't-tllClllt condition and to retain the circuit breaker in closed position so long as the value of the current passing below a predetermined amount.

It will be understood that the bimetal element is normally connected in series with the circuit-breaker contacts and is heated by the current flowing through the circuit breaker contacts to the motor or lamp circuit to which the circuit breaker connected. It will be further understood that the circuit breaker is trip-free of the handle and, therefore, the handle cannot interfere with the opening movement of the circuit breaker in response to an overload or shortcircuit condition, regardless of its position, or whether it is being held by the operator.

In practice, it has been found that a small circuit breaker of the character disclosed in the above-noted copcnding application and described herein, may be conveniently and economically provided with thermal elements capable of causing the circuit breaker to open under currents slightly in excess of ampcres or amperes, depending upon the predetermined capacity of the thermal element employed.

Circuit breakers having a current-carry- 30 ampercs may, therefore, be provided with a lo-ampere-capacity thermal element for use in distributing panels of house-wiring circuits, and with thermal elements of 30-an1pere capacity when used as entrance circuit breakers. Because of the large demand for. circuit breakers of the 15 and EEO-ampere capacity and because the circuit breaker unit isthe same in both cases, with the exception of the thermal element, the circuit breakers may be manufactured on a quantity-production basis, with the result that the manufacturing cost is materially reduced.

There are, however, certain fields of activity that require circuit breakers which will open the circuit under current values considerably leSs than 15 amperes, and there is also a demand for circuit breakers for circuits having apparatus that requires protection at current values considerably above 30 amperes.

It is an object of my invention to provide a circuit breaker wherein standard circuit breaker units having the characteristics of circuit breakers above described and which may be manufactured on a qinintity-production basis, may be used in circuits requiring rotect-ion at current values considerably less and considerably greater than those for which the standard circuit breaker is designed.

In Fig.3, I have diagrammatically shown a circuit breaker having a bimetal thermal element 26 that is designed to cause the circuit breaker to open when an overload slightly exceeding 15 amperes occurs. In order to adapt the circuit'breaker for use in a circuit wherein the current must not exceed 3 amperes, for example, I have provided an auto-transformer which may be of any preferred construction and may have a winding 33 and the usual iron core (not shown).

The bimetal element 26 is connected, at one terminal, to one end of the winding 33 and to the switch arm 14, and the other terminal of the bimetal element is connected to a tap connection 34 that may be connected to the winding 33, at any predetermined point, to obtain the desired operating result.

The auto-transformer employed is of such design that it will, at operating voltage, permit the required current to flow therethrough with but little impedance. By reason of the manner in which the thermal element 26 is connected to the winding 33, a circuit is established which includes the thermal element and through which current will circulate having a value determined by the relative position of the tap connection 34 with respect to the coils of the winding 33. If it is desired to cause the thermal element 26, which is designed to trip the circuit breaker to open position under a load slight- 1y greater than 15 amperes, to trip the circuit breaker to open position when the current value slightly exceeds three amperes, the tap 34 is adjusted to include sufficient turns of the winding 33 between the terminals of the thermal element to set up a current through the thermal element corresponding to that required to cause its operation under a load slightly greater than 15 amperes. By reason of this arrangement of the bimetal element and its associated auto-transformer, a l5-am )ere-capacity thermal element may be used to operate under a current value of three or less amperes, if desired.

Since the auto transformer is connected in series with the circuit break r. it also serves to limit the current passing through the circuit breaker at the time of opening under severe overload or short-circuit surges.

In Fig. 4, I have diagrammatically illustrated a thermal bimental element of 30-amperes capacity, so connected to an auto-.

transformer 33 that it may be used in a circuit breaker that is connected in a circuit normally carrying 60 amperes. In this construction, the feed conductor 35 is so connected to the tap connection 34 that the feed conductor may be connected to the winding 33 at an desired point intermediate the ends of t e winding. The terminals of the p bimetal element 26 are connected across the extreme ends of the winding 33. In this arrangement, the current of 60 amperes may be so divided that substantially 3O amperes flows through the bimetal element 26 and substantially 30 amperes flows throu h the right-hand end of the winding 33. y adjusting the tap connection 34 to certain positions on the winding 33, the proportion of the current supplied to the thermal element 26 may be varied, and, therefore, the circuit breaker may be made to trip open by current values ranging from 30 to 60 amperes. The auto-transformer, in this case should, however, be lesigned to pass '60 amperes of current with a minimum of impedance.

In Fig. 5, I have illustrated the manner in which two circuit-breaker 'units may be connected in parallel in a circuit for doubling the capacity of the circuit breaker. For instance, if two 30-ampere-capacity circuit breakers are connected in parallel, they will function to open the circuit when the load exceeds 60 amperes, provided the current is egiually divided between them. Since it is di breakers that have exactly the same contact resistance and the same thermal element resistance, it is necessary to determine their relative conductivity and provide means for equalizing the current supplied to each of them and their thermal elements in order that one of them shall not carry more of the load than the other and thus cause premature opening by reason of over-heating. I have, therefore, provided an auto-transformer winding 33 with a tap connection 34 to which the feed conductor 35 is connected, the tap connection being located at the point where the required distribution of the current is accomplished.

It will be understood that, where a plurality of circuit breakers of the trip-free of the handle type are utilized, a single operating handle 29 is provided that is connected to an insulating bar 36 which is connected to the operating levers 27 of the several circuit breakers, as indicated in Fig. 2, wherein, three circuit breakers are shown connected in parallel in a single circuit.

In the event that one of the thermal elements 26 releases its circuit breaker before the other circuit breaker is opened, the sud,- den increase of current through the other circuit breaker and thermal element will almost instantly cause the remaining circuit breaker to open because it is already on the vergeof opening at the time the first circuit breaker is released.

By reason of this arrangement of the thermal elements of two circuit breakers with cult to manufacture two circuit an auto-transformer, it is possible to connect a -ampere thermal element and a 30-11mperc thermal element in such manner that they will both function to open the circuit simultaneously, under a predetermined load condition.

In Figs. 6 and 7, I have illustrated the manner in which a group of three and four separate circuit-breaker units may be connected in a. single circuit, and the current distributed as desired, through the medium of auto-transformers, to obtain the desired operating characteristics of the circuit breaker. By combining three circuit breakers, each having 30-ampere-capacity thermal elements, a 90-ampere circuit breaker may be produced and. by combining four 30- ampere circuit breakers of 30-ampere capacity, a 120-ampere circuit breaker may be obtamed.

In Figs. 1 and 2. I have shown a circuit breaker of the 90-21mpere-capacity type which comprises three 30-ampere-capacity circuit-breaker units. The units are mounted within a metal housing 37 having a cover 38 that may be sealed in closed position and is provided with a slot 39, through which the operating handle 29 projects. The two auto-transformers 33 required for the arrangement illustrated diagrammatically in Fig. 6 are mounted in the same housing with the circuitl.-real-:er units and are therefore, protected from external objects and from tampering therewith.

Ithas been found that a circuit breaker that has been constructed by combining two or more 15 or 30-ampere circuit-breaker units is considerably less expensive than a single circuit breaker having a capacity equal to that of the combined units. A circuit breaker of relatively large capacity usually requires a blow-out coil or' other relatively expensive means for extinguishing the are drawn between the contacts when the circuit breaker opens. In the case of the small circuit breaker units, connected in parallel in a single circuit, the arcs drawn are relatively small and are readily extinguished without the necessity t" r a blow-out coil or like extinguishing device. As briefly pointed out. because of the quantity production of the small units, the manufacturing cost is materially reduced.

In Fig. 8. I have disclosed the manner in which a three-phase circuit breaker is arranged by providing three parallel-connected circuit-breaker units for each phase of the circuit and by providing the necessary auto-transformers 33 for distributing the current between the circuit breakers of each phase. In this arrangement, nine circuitbreaker units and six auto-transformers 33 are required. The operating bar 36 extends across the circuit-breaker units and is connected to each of the operating levers of the nine circuit breakers. Since the individual circuit-breaker umts are all trip-free of the handle, theymay trip opcn without etfecting the other circuit breakers connected in or some other form of transformer wherein the primary and secondary windings are separate and of the inductive type.

Other forms of current-rcsponsive devices may also be used, and various changes, modifications. substitutions, additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. The combination with a circuit breaker having a current-responsive thermal tripdevice connected in series with the contacts thereof, of an auto-transformer connected in series with the circuit-breaker contact for controlling the supply of current to the said trip-device.

2. The combination with a plurality of circuit breakers each having a currentresponsive thermal trip-device connected in series with the contacts of its respective circuit breaker, the said trip-devices being connected in parallel. of means for dividing the current among the current-respoiisive devices in predetermined proportions.

3. The combination with a plurality of circuit breakers each having a current-responsive thermal trip-device in series with.

its respective circuit breaker, of means, including auto-transformers for dividing the current among the current-responsive devices in predetermined proportions.

4. The combination with a plurality of circuit breakers connected in parallel in a. single circuit and each having a currentresponsive thermal trip-device connected in series with the contacts of its respective circuit breaker, the said trip-device being connected in parallel, of means for supplying current to the trip devices in predetermined proportions.

The combination with a plurality of circuit breakers connected in parallel to a single circuit and each having a current-responsive thermal trip device in series with the corresponding circuit breaker, of means for supplying current to the trip device in predetermined proportions, and a manually operable means for simultaneously operating the circuit breakers that is trip-free from all of the said circuit breakers.

6. A pol phase circuit breaker comprising a plura ity of circuit breakers connected in parallel in each phase and having a common manually operable means for operating 5 the circuit breakers that is trip free from all of them, a separate current-responsive thermal trip-device for each circuit breaker for each phase, and means for supplying current to the said trip-devices in prede- 31 termined proportions. 1 p

7. In a circuit interrupter, a plurality of switch arms connected in parallel in a single circuit,v a single operating means for normally actuating all of said switch arms, a

plurality of current-responsive thermal trip elements each connected in series with one of said switch arms, and means for dividing the current amongsaid trip elements in predetermined proportions.

8. Ina circuit interrupter, a plurality of switch arms connected in parallel in a single circuit, a single operating means for normally actuating all of said switch arms, a plurality of current-responsive thermal trip elements each connected in series with one of said switch arms and all of said switch arms being caused to open substantially simultaneously upon the flow of a predetermined current through one of said trip elements, and a transformer for causing current to flow through said trip elements in predetermined proportions.

9. In a circuit interrupter, a plurality of switch arms connected in parallel in a single circuit, a single operating means for normally actuating all of said switch arms to both open and closed ositions and said switch arms being mova le to open position irrespective of the position of said operating means, a plurality of current-responsive thermal trip elements each connected in series with one of said switch arms and all of said switch arms being caused to 0 en substantially simultaneously upon the ow of a predetermined current through one of said trip elements, and an auto-transformer for dividing the current flowing in said single circuit between said trip elements in predetermined proportions.

In testimony whereof, I have hereunto subscribed my name this 31st day of March,

KARL C. RANDALL. 

